The present invention relates to a micro-climate heating and cooling method and to a device that is lightweight, needs only a small, battery-operated pump as the only moving component, and is regeneratable. More particularly, the present invention relates to a system and method in which heating or cooling is generated by reaction of water vapor or other working fluid with an adsorbent material and which does not require the use of refrigeration to keep phase-change material cold. The present invention is especially appropriate for micro-climate cooling and heating of soldiers wearing NBC overgarments, cooling systems for firefighters, nuclear power workers, foundry workers, and construction workers, and for a passive cooling system used by race car drivers and configured to be lighter than the currently used ice water cooling systems.
The passive cooling approach available up to now has been the use of a phase change material that "melts" and adsorbs body heat as shown in U.S. Pat. No. 4,856,294. Passive methods have not, however, generally been used for heating. Heating can be accomplished by use of a phase change material that is melted so as to provide heat to the body by recrystallization. Although this heating approach works, the weight penalty becomes prohibitive for heating or cooling times greater than one hour and is, therefore, unacceptable for long periods of use.
An active refrigeration system is known for cooling in which a fuel is used to power an active air conditioning system. More specifically, a vapor-compression-type system is used in which the fuel powers an engine to provide shaft work which, in turn, drives a compact vapor-compression-air conditioning system, thereby achieving the cooling. Such a system is superior to Stirling or Brayton cycle approaches in terms of efficiency and weight. Today's technology for the internal combustion power source dictates, however, an approximate engine mass of 3 pounds, which consumes approximately 6 pounds of fuel during a 6-hour cooling period. In addition, all of these known active systems produce an unacceptable level of noise due to the engine.
It is, therefore, an object of the present invention to solve the problems of weight, noise, and the like for heating and cooling requirements which exceed short periods of time, i.e. periods in excess of one hour and up to about six hours.
These problems have been solved in accordance with the present invention by the utilization of a body temperature control system that is regeneratable and uses a lightweight, battery-operated circulating pump as the only moving component to provide both the heating and the cooling requirements. Two heat exchangers are used, one in the water reservoir for cooling and a second in the adsorption bed for heating.
Inasmuch as a heating or cooling requirement is not continuous but instead is only needed for six hours due primarily to protective capacity time constraints, an intermittent air conditioner in accordance with the present invention offers improved mass, noise, and reliability features.
One presently contemplated embodiment of the present invention includes a water-filled vest for both heating and cooling. The vest is configured with a small battery-operated circulating pump for either the heating system or the cooling system. The systems can supply up to 300 watts of cooling or 540 watts of heating for a period of up to six hours as maximum design requirements. The user-controlled needle valve is used to control a vest temperature, even under varying heating or cooling requirements, up to the maximum design cooling requirement of 300 watts or maximum design heating requirement of 540 watts for six hours. After the six-hour heating or cooling period, the backpack is removed and recharged on a recharge stand by heating either electrically with, for example, resistance heaters/multiple voltage operation or by using fuel in a ceramic-wick, e.g. a kerosene heater-type configuration. The fuel for the ceramic wick is, for example, a JP-8-type kerosene fuel. Of course, the present invention can also be used in either types of clothing, e.g. gloves, without departing from its inventive principles.
Another advantage of the present invention in the form of a personal heating/cooling device resides in the fact that only one moving part is needed, namely, a battery-operated circulating pump. The cooling system evaporates the water from a sealed reservoir and captures this water in an adsorption bed that rejects heat to the environment. The rate of adsorption of water vapor on the bed is very fast, and a user-controlled needle valve between the water reservoir and the adsorption bed controls the evaporation to maintain the desired amount of cooling or heating. A heat exchanger in the water reservoir cools the circulating water in the water-vest heat exchanger. The heating system adsorbs water onto the desiccant bed and then pumps the heat generated through a heat exchanger to a water-vest heat exchanger.